EP0021012B1 - Process for preparing para-substituted aromatic carbamic acid esters - Google Patents

Description

The invention relates to a new process for the preparation of p-substituted aromatic carbamic acid esters by reacting aromatic carbamic acid esters with olefins in the presence of inorganic acids or sulfonic acids.

It is known from Houben-Weyl, Methods of Organic Chemistry, Volume 11/1, pages 137 to 145 to prepare aromatic carbamic acid esters by reacting the corresponding aromatic amines with chloroformic acid ester in the presence of an acid-binding agent or by reacting the corresponding aryl isocyanates with alcohols. The main disadvantage of these processes is that they start from the para-ring alkylated anilines which are known to be difficult to access. US 2,695,913 describes the production of special alkylaryl urethanes from alkylaryl isocyanates and polyoxy compounds e.g. B. polyoxyalkylene glycols. The required alkylaryl isocyanates are produced by known methods, namely by acid-catalyzed alkylation of aromatics, nitration with nitric acid / sulfuric acid, catalytic reduction with hydrogen and subsequent phosgenation of the amines. All of these methods are unsatisfactory in terms of yield and simple and economical operation.

worin die einzelnen Reste R^l, R², R³, R⁴, R⁵ und R⁶ gleich oder verschieden sein können und jeweils einen aliphatischen Rest bedeuten, R^l, R² und R³ auch jeweils einen WB/BL cycloaliphatischen, araliphatischen oder aromatischen Rest bezeichnen, jeweils 2 der Reste R^l, R² und R³ auch zusammen mit den benachbarten Kohlenstoffatomen für Glieder eines alicyclischen Ringes oder R', R² und R³ auch zusammen mit den benachbarten Kohlenstoffatomen für einen bicyclischen Rest stehen, R², R³ und R⁵ auch jeweils ein Wasserstoffatom bezeichnen, R⁴ auch ein Wasserstoffatom oder ein Halogenatom bedeutet, R⁸ auch einen cycloaliphatischen Rest bezeichnet, vorteilhaft erhält, wenn man aromatische Carbaminsäureester der Formel

worin R⁴, R⁵ und R⁶ die vorgenannte Bedeutung besitzen, mit Olefinen der Formel

worin R¹, R² und R³ die vorgenannte Bedeutung besitzen, in Gegenwart von anorganischen Säuren oder Sulfonsäuren umsetzt.It has now been found that p-substituted aromatic carbamic acid esters of the formula

wherein the individual radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ^{6 may be the} same or different and each represent an aliphatic radical, R ¹ , R ² and R ³ also each have a WB / BL cycloaliphatic, araliphatic denote or aromatic radical, in each case 2 of the radicals R ¹ , R ² and R ³ together with the adjacent carbon atoms also represent members of an alicyclic ring or R ', R ² and R ³ also together with the adjacent carbon atoms represent a bicyclic radical, R ² , R ³ and R ⁵ also each denote a hydrogen atom, R ⁴ also denotes a hydrogen atom or a halogen atom, R ⁸ also denotes a cycloaliphatic radical, advantageously obtained if aromatic carbamic acid esters of the formula

wherein R ⁴ , R ⁵ and R ^{6 have} the abovementioned meaning, with olefins of the formula

where R ¹ , R ² and R ^{3 have} the abovementioned meaning, in the presence of inorganic acids or sulfonic acids.

If the N-phenylcarbamic acid ethyl ester and isobutene are used, the reaction can be represented by the following formulas:

Compared to the known processes, the process according to the invention surprisingly provides a large number of p-substituted aromatic carbamic acid esters in a better space-time yield and purity, in a simpler and more economical way, especially on an industrial scale and in continuous operation. It was surprising that p-substitution of an N-arylcarbamic acid ester could already be carried out in good yield with catalytic amounts of an acid. In view of the teaching that carbamic acid esters are cleaved in the presence of acids (Houben-Weyl, Volume 11/1, pages 948), it was also not to be expected that the substitution in the presence of acids without the formation of heterogeneous mixtures with substantial amounts of by-products is feasible.

The olefin III can be reacted with the aromatic carbamic acid ester II in a stoichiometric amount, in excess or in excess, preferably in a ratio of 0.3 to 5, in particular 0.5 to 4, moles of olefin per mole of carbamic acid ester II. Preferred aromatic carbamic acid esters II, olefins III, and accordingly preferred aromatic carbamic acids I are those in the formulas of which the individual radicals R ¹ , R ² , R ³ , R ⁴ , R ⁵ and R ^{6 can be the} same or different and each have an alkyl radical 1 to 10, in particular 1 to 4 carbon atoms, R ¹ , R ² and R ³ also each denote a cycloalkyl radical with 5 to 8 carbon atoms, an aralkyl radical or alkylaryl radical with 7 to 12 carbon atoms or a phenyl radical, each 2 of the radicals R ¹ , R ² and R ³ also together with the adjacent carbon atoms for members of an alicyclic ring with 5 to 8 carbon atoms or R ¹ , R ² and R ³ also together with the adjacent carbon atoms in the starting material II for norbornene and in this case in the end product I for one Are norbornyl, R ² , R ³ and R ⁵ each also denote a hydrogen atom, R ⁴ also denotes a hydrogen atom or a bromine atom or a chlorine atom, R ⁶ also denotes a cycloalkyl radical having 5 to 8 carbon atoms. The aforementioned radicals and rings can still by groups inert under the reaction conditions, for. B. alkyl groups or alkoxy groups having 1 to 5 carbon atoms, the phenyl radical substituting chlorine or bromine atoms, may be substituted.

Branched alkenes are preferably used. In contrast to the known processes, mixtures of alkenes and, if appropriate, of alkenes with alkanes, such as those used e.g. in the cracking or dehydrogenation of hydrocarbons, e.g. As petroleum, or the oligomerization of olefins, in particular isobutylene, propylene or n-butene, or the carbon oxide hydrogenation. Instead of the olefins it is also possible to use olefin-forming compounds under the reaction conditions, for example ethers such as methyl tert-butyl ether, esters such as tert-butyl acetate or alcohols such as tert-amyl alcohol or tert-butanol.

It can e.g. B. the following olefins are used as starting materials II: n-pentene (1), n-hexene (1), n-heptene (1), n-octene (1), n-nonene (1), n-decen- (1), n-undecen- (1), n-dodecen- (1), propylene- (1). n-butene- (1); aforementioned alkenes in the 2-position or 3-position or 4-position by the methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl Group are substituted; 2,3-dimethyl-n-butene, 3,3-dimethyl-n-butene, 2-methyl-3-ethylpentene, 3-methyl-3-ethylpentene, 2,3,3-trimethylheptene, 2,4,4- Trimethylpentene, 2,3,3-trimethylpentene, 2,3,4-trimethylpentene; analog alkenes whose double bond is in the 2-position or in the 3-position in the molecule; branched alkenes, such as those obtained in the form of mixtures in the dimerization of isobutylene or n-butene (octenes) or trimerization of isobutylene or n-butene (dodecenes) or propylene (nonenes) or tetramerization of propylene (dodecenes); o-methylstyrene, m-methylstyrene, p-methylstyrene, 3,5-dimethylstyrene, o-ethylstyrene, m-ethylstyrene, p-ethylstyrene, 4-chlorostyrene; Cycloheptene, a-methylstyrene, norbornene, cyclohexene, 1-methylcyclohexene.

Preferred are: propylene, isobutylene, styrene, n-octenes, n-nonenes, n-decenes and n-dodecenes, 2,3-dimethylbutene-1, 2-methylbutene-1,2-methylbutene-2, n-butene, 2 -Ethylbutene-1, cyclopentene, cyclohexene, «methylstyrene, norbornene.

For example, the following aromatic carbamic acid esters II are suitable: methyl phenylcarbamate; in the 2-, 3-, 5-, 6-position single or in the 2,3-, 2,5-, 2,6-position twice the same or different by a chlorine atom, a bromine atom, the methyl, ethyl, propyl -, Isopropyl, butyl, isobutyl group substituted phenylcarbamic acid methyl ester; corresponding N-methyl, N-propyl, N-ethyl, N-isopropyl, N-butyl, N-isobutyl-phenylcarbamic acid methyl ester; homologous ethyl, propyl, isopropyl, butyl, isobutyl, cyclohexyl, cyclopentyl, cycloheptyl, cyclooctyl esters; preferred are: phenyl, o-tolyl, m-tolyl, o-chlorophenyl, m-chlorophenyl, o-ethylphenyl, o-propylphenyl, 2-chloro-6-methylphenyl, 2-chloro-5 -methylphenyl, 2,6-dimethylphenyl or 2,5-dimethylphenylcarbamic acid methyl ester and the corresponding ethyl, propyl, butyl or cyclohexyl ester.

The reaction is generally carried out at from 25 to 160.degree. C., preferably from 40 to 150.degree. C., in particular from 60 to 130.degree. C., with reduced pressure, excess pressure or without pressure, preferably at a pressure of 1 to 30 bar, preferably up to 20 bar, carried out continuously or discontinuously. The residence time is preferably from 0.5 to 10, in particular from 0.5 to 5 hours, the throughput is preferably from 1 to 120, in particular from 5 to 50, kg of starting material II per kg of catalyst and hour. It is advisable not to use additional solvents; if necessary, but also come, for. B. to lower the viscosity of the reaction mixture, under the reaction conditions inert solvents into consideration. As a solvent such. B. in question: aliphatic or cycloaliphatic hydrocarbons, e.g. B. heptane, nonane, gasoline fractions within a boiling point interval of 70 to 190 ° C. Cyclohexane, methylcyclohexane, decalin, petroleum ether, hexane, ligroin, 2,2,4-trimethylpentane, 2,2,3-trimethylpentane, 2,3,3-trimethylpentane, octane; Halogenated hydrocarbons, especially chlorinated hydrocarbons, e.g. B. tetrachlorethylene, 1,1,2,2-tetrachloroethane or 1,1,2,2-tetrachloroethane, dichloropropane, methylene chloride, dichlorobutane, chloroform, carbon tetrachloride, tetrachloroethane, 1,1,1-trichloroethane or 1,1,2- Trichloroethane, trichlorethylene, chlorobenzene, pentachloroethane, cis-dichloroethylene, 1,2-dichloroethane, 1,1-dichloroethane; aromatic hydrocarbons, e.g. B. benzene, toluene, xylenes; Tetrahydrofuran, dioxane, methyl acetate; and corresponding mixtures. The solvent is expediently used in an amount of 10 to 1,000 percent by weight, preferably 50 to 200 percent by weight, based on starting material 11.

The reaction is carried out in the presence of catalysts in the form of inorganic acids or sulfonic acids, advantageously in an amount of from 0.01 to 0.5, in particular from 0.05 to 0.3, equivalents of acid, based on one mole of starting material II. Instead of monobasic acids, equivalent amounts of polybasic acids can also be used. For example, the following acids are suitable: hydrogen chloride, sulfuric acid, phosphoric acid; Sulfonic acids such as methane, benzene and p-toluenesulfonic acid; Hydrofluoric acid; or corresponding mixtures. The acids can be used in concentrated form, in a mixture with one another and / or with a solvent.

Organic, sulfonic acid cation exchangers, preferably resins made from sulfonated polystyrene divinylbenzene, sulfonated, crosslinked styrene polymers, are preferably used as catalysts; sulfonic acid phenol formaldehyde or benzene formaldehyde resins; perfluorinated, sulfonated polystyrene-divinylbenzene resins; perfluorinated, sulfonated, cross-linked polystyrene resins, or copolymers of tetrafluoroethylene and vinyl sulfonic acid. Sulfonated polystyrene-divinylbenzene exchangers are preferred. The exchangers are in the acid form and not as salt. Depending on its application, the catalyst advantageously has a particle size of 5 to 2000, preferably 10 to 1800, advantageously 20 to 1500 micrometers. It can have both a macroporous and a gel-like structure. Are suitable for. B. exchange resins, such as those under the designation ^(R) LEWASORB A-10, ^(R) LEWATIT SPC-118, ^(R) AMBERLYST 15, ^(R) AMBERLIT IR-120, ^(R) DOWEX 50, ^(R) LEWATIT S -100, ^(R) NALCITE HCR, ^(R) PERMUTIT RS, ^(R) WOLFATIT KPS-200 are commercially available. It is conveniently dewatered before use in a conventional manner, e.g. B. by heating to 100 ° C to 110 ° C in a vacuum. However, dehydration can also be carried out by displacement with hydrophilic organic liquids and subsequent heating to 100 ° C. under reduced pressure or by azeotropic distillation with an organic liquid.

The catalyst in the form of an ion exchanger can be in any discontinuous or continuous procedure, for. B. in the form of a fixed bed can be used. It is also advantageously in suspension during the reaction, usually in the reaction mixture which forms. A proportion of liquid carbamic acid ester II and olefin III and, if appropriate, solvent is advantageously introduced and the catalyst is suspended in the liquid with thorough mixing. It is advantageous to choose the amount of carbamic ester II or starting mixture and / or organic solvent provided in such a way that the catalyst in the form of an ion exchanger in the reaction mixture which is formed in an amount of 0.3 to 30, preferably 1 to 20 percent by weight, based on the weight of the entire liquid mixture in the reaction chamber is suspended. An amount of from 1 to 70, in particular from 10 to 50, percent by weight of ion exchanger, based on carbamic acid ester, is preferred. The reaction mixture is expediently mixed throughout the entire reaction, preferably at a stirring speed of at least 100, advantageously from 200 to 2000, in particular from 300 to 1000 revolutions per minute. With mixing devices without agitator, e.g. B. even with mixing by means of inert gas such as nitrogen, those are preferred which bring the aforementioned stirring speed corresponding shear energy. A finely dispersed suspension is achieved in this way.

The reaction can be carried out as follows: A mixture of starting material II and III, catalyst and optionally solvent is kept at the reaction temperature during the reaction time. After removal of the catalyst, the end product can be used in a conventional manner, e.g. B. by filtration and distillation.

The reaction can be carried out in the case of using ion exchangers as catalysts and in continuous operation in a fixed bed or advantageously as follows: A liquid mixture of carbamic acid ester, olefin, optionally together with solvent, is at the reaction temperature and the reaction pressure by a suspension of the catalyst in Starting mixture or reaction mixture passed and filtered. Then the end product from the reaction mixture in a conventional manner, for. B. separated by distillation. The filtration is expediently carried out before the suspension emerges from the reactor. Acid-resistant filter cloths, wire mesh filters and sintered metal filters are suitable as filters, provided the mesh sizes or pore diameters are smaller than the catalyst particles.

The aromatic carbamic acid esters I which can be prepared by the process of the invention are active ingredients and valuable starting materials for the production of dyes, pesticides and pharmaceuticals. By hydrolysis of the carbamic acid esters (Houben-Weyl, Volume 11/1, pages 448 to 952), the corresponding anilines can be prepared, which are also important starting materials in the synthesis of active ingredients. Regarding the use, reference is made to the aforementioned Publications, OE-PS 183416 and Ullmann's Encyclopedia of Industrial Chemistry, Volume 5, pages 73 to 76.

The parts listed in the following examples are parts by weight. They relate to parts by volume like kilograms to liters.

example 1

A suspension of 165 parts of ethyl N-phenylcarbamate and 50 parts of exchange resin is prepared in a stirred reactor at a stirring speed of 300 revolutions per minute at 120 ° C., and 100 parts of isobutene are pumped in over the course of 2 hours. A pressure of 2 bar is set by pumping in isobutylene. The exchange resin is a sulfonated resin copolymerized from styrene and divinylbenzene, which is dewatered in vacuo at 100 ° C for 24 hours before use; it has a grain size of 0.5 to 1.5 millimeters. Now the suspension in the reactor is constantly stirred at 500 revolutions per minute. After 2 hours at 120 ° C, the suspension is filtered and fed to a fractional distillation. 170 parts (77% of theory, based on the N-phenylcarbamic acid ethyl ester) of N- (4-tert-butylphenyl) carbamic acid ethyl ester of bp 125 ° C-127 ° C (0.2 mbar) are obtained. The conversion is 80 percent (based on the carbamic acid ester 11).

Example 2

A suspension of 165 parts of ethyl N-phenylcarbamate and 30 parts of exchange resin is prepared in a stirred reactor at a stirring speed of 300 revolutions per minute at 100 ° C. and 130 parts of styrene are fed in at 1 bar within one hour. The exchange resin is a sulfonated resin copolymerized from styrene and divinylbenzene, which is dewatered in vacuo at 100 ° C for 24 hours before use; it has a gel structure and a grain size of 20 to 150 micrometers. Now the suspension in the reactor is stirred at 100 ° C. for one hour at 300 revolutions per minute. The catalyst is then separated off, unreacted starting material is distilled off in vacuo and the residue is recrystallized from cyclohexane. 240 parts (89% of theory, based on the carbamic acid ester) of N- (4- (α-methylbenzyl) phenyl) carbamic acid ethyl ester of mp 78 ° to 80 ° C. are obtained. The turnover is 90 percent.

Example 3

A suspension of 165 parts of ethyl N-phenylcarbamate and 50 parts of exchange resin is prepared in a stirred reactor at a stirring speed of 300 revolutions per minute at 120 ° C. and 100 parts of 2-methylbutene-2 are fed in at 1 bar at 2 bar. The exchange resin is a sulfonated resin copolymerized from styrene and divinylbenzene, which is dewatered in vacuo at 100 ° C for 24 hours before use; it has a gel structure and a grain size of 20 to 150 micrometers. Now the suspension is stirred in the reactor at 300 revolutions per minute at 120 ° C. for 2 hours. The catalyst is then filtered off and distilled in vacuo. 195 parts (82% of theory, based on the carbamic acid ester II) of N- (4-tert.-amylphenyl) carbamic acid ethyl ester of bp 145 to 147 ° C. (0.3 mbar) are obtained. The conversion is 84 percent (based on the carbamic acid ester 11).

Example 4

In a stirred reactor, a mixture of 165 parts of N-phenylcarbamic acid ethyl ester and 10 parts of sulfuric acid (96 percent) is heated to 70 ° C. with stirring and 104 parts of styrene are added over the course of two hours. After the styrene addition has ended, the mixture is stirred at 70 ° C. for a further two hours. The mixture is then diluted with 100 parts of toluene, neutralized with aqueous sodium carbonate solution and distilled in vacuo. After recrystallization from cyclohexane, 185 parts (69% of theory, based on the carbamic acid ester II) of N- (4- (a-methylbenzyl) phenyl) carbamic acid ethyl ester of mp 78 ° to 80 ° C. are obtained. The turnover is 75 percent.

Example 5

A mixture of 165 parts of ethyl N-phenylcarbamate and 10 grams of p-toluenesulfonic acid is heated to 100 ° C. with stirring in a stirred autoclave and 112 parts of isobutene are pumped in over the course of two hours. After the addition of isobutene has ended, the mixture is stirred at 100 ° C. for a further two hours. The mixture is then diluted with 100 parts of toluene, extracted with aqueous sodium carbonate solution and the end product is distilled in vacuo. 169 parts (72% of theory, based on the carbamic acid ester II) of N- (4-tert-butylphenyl) carbamic acid ethyl ester of bp 125 to 127 ° C. (0.2 mbar) are obtained. The turnover is 76 percent.

Claims (1)

1. A process for the preparation of a p-substituted, aromatic carbamic acid ester of the formula

   

   where the individual radicals R¹, R², R³, R⁴, R⁵ and R⁶ may be identical or different and each is an aliphatic radical, R¹, R² and R³ may also each be a cycloaliphatic, araliphatic or aromatic radical, any 2 of the radicals R¹, R² and R³ may also, conjointly with the adjacent carbon atoms, be members of an alicyclic ring, R¹, R² and R³ conjointly with the adjacent carbon atoms may also be a bicyclic radical, R², R³ and R⁵ may also each be hydrogen, R⁴ may also be hydrogen or halogen and R^B may also be a cycloaliphatic radical, wherein an aromatic carbamic acid ester of the formula

   

   where R⁴, R⁵ and R⁶ have the above meanings, is reacted with an olefin of the formula

   

   where R¹, R² and R³ have the above meanings, in the presence of an inorganic acid or sulfonic acid.